Bulova Watch Company 605
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|Manufacturer:||Bulova Watch Company|
READING TAKEN WITH WESTON MODEL 565 ANALYZER
Line Voltage 115. Order of Test: 1 Rect., 2 Power, 3 Det., Etc.
Volume Control Position, Full On.
NOTE: Since resistance tolerances in the sets are plus or minus 10% and tubes may vary over 20% your readings may disagree with the above by plus or minus 30%.
Number 1 is the antenna trimmer.
Number 2 is the gang condenser trimmer tuning the grid of the Super-autodyne.
Number 3 is the gang condenser trimmer tuning the plate (or oscillator of the super autodyne).
Number 4 is the oscillator padding trimmer.
Number 5 is the Super-autodyne plate trimmer.
Number 6 is the I. F grid trimmer.
Number 7 is the second detector grid trimmer.
To readjust the trimmer, it will be necessary that a good design of 175 k. c. oscillator be employed, and that a dependable broadcast test Oscillator be on hand so that stages handling intermediate frequency, and those handling radio frequency can be thoroughly checked. It is advisable to use a bakelite screwdriver when making any of these adjustments.
First, connect the 175 k. c. oscillator output leads from the control grid cap of the super autodyne tube to ground. Do not remove any of the tubes from the sockets, and it is not necessary to disconnect the grid cap clip from the tube. Reset trimmers numbers 5,6 and 7 for maximum output. While this test oscillator is working into the intermediate frequency stages, no adjustment of the tuning condenser on the receiver will have any effect, inasmuch as the intermediate frequency stage is fixed tuned.
If your test oscillator is properly designed, it will supply exactly 175 k. C., and when trimmers number 5,6 and 7 are set for maximum output, they will be correctly adjusted and should be sealed.
Next, disconnect the 175 k. c. test oscillator and connect to the antenna binding post of the receiver, the output lead from your broadcast test oscillator, or tune in a broad cast signal around 1400 k. c., then reset trimmers numbers 2 and 1 respectively for maximum output. This adjustment will tract the super-autodyne grid circuit of the R. F stage.
To check the calibration of the receiver whether it be high or low, trimmer number should be reset until a station of known nigh frequency is brought in on the correct dia marking with peak volume. If your broadcast test oscillator is accurately calibrated, it might be used in place of the broadcasting station signal. In this adjustment, a broad cast station or test oscillator signal at about 1400 k. c. should be chosen. The setting of the trimmer at 1400 k. c. is more critical than it would be at 600 k. c.; calibration therefore more accurate.
The next adjustment is important and not easily explained in writing, so pay close attention to the following instruction. will now balance the oscillator to the r. f and first detector stages.
Tune the external broadcast test oscillator and the receiver both to 600 k.c., then slowly increase or decrease the capacity of No. 4 (oscillator padding trimmer), at the same time and continuously tuning back and forth across the signal with the receiver tuning condenser gang, The output meter needle will now be swinging up and down in step with the variation in tuning. Watch the peak of this swinging closely and readjust No. 4 trimmer until the swinging needle reaches its highest peak.
Retune the receiver and broadcast test oscillator to 1400 k.c. and re-check trimmer No. 3 to make sure that the adjustment of No. 4 has not thrown the receiver out of calibration. If it has, then readjust No. 3 until the calibration is correct, (as previously explained), and check on trimmers No. 2 and No. 1, to make sure that the adjustment of No. 4 has not reduced the sensitivity.